The declining mountain snowpack is expected to melt earlier and more slowly with climate warming. Previous work indicates that lower snowmelt rates are associated with decreased runoff. However, earlier snowmelt could increase runoff via lower vegetation water use in early spring. The relative importance of these factors with regard to runoff is linked to site‐specific conditions such as plant available water storage (PAWS) and energy availability. To disentangle the effects of snowmelt rate and timing on runoff production, we conducted a hydrologic modeling experiment at sites in Colorado (NR1) and California (P301) that controlled for snowmelt rate and timing multicollinearity. We tested the sensitivity of snowmelt season potential runoff (R), changes in subsurface storage (ΔS), and other water budget components to snowmelt rate (sm_r) and timing (sm_t) using multiple linear regression and global sensitivity analysis (GSA). Regression results confirmed that R was governed by the competing influence of sm_r and sm_t. At both sites, ΔS was more sensitive to sm_t than sm_r while R was more sensitive to sm_r at P301 and to sm_t at NR1, reflecting energy limitation at NR1. GSA analyses mirrored the regressions for R, confirming that sm_t was more important at NR1 than P301. This work suggests that runoff increases from earlier snowmelt may counteract runoff losses due to slower snowmelt and that this process is mediated by PAWS and energy availability. These results suggest that R will be more susceptible to future changes in sm_r and sm_t at sites with greater PAWS and available energy.

中文翻译：

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融雪率和时间对径流的抵消作用

随着气候变暖，下降的山脉积雪预计会融化得更早，更慢。先前的研究表明，较低的融雪速率与径流减少有关。但是，较早融雪可能会通过减少早春的植被用水来增加径流。这些因素在径流方面的相对重要性与特定地点的条件有关，例如工厂可用的水存储（PAWS）和能源的可用性。为了弄清融雪速率和时间对径流产生的影响，我们在科罗拉多州（NR1）和加利福尼亚（P301）的地点进行了水文模拟实验，控制融雪速率和时间的多重共线性。我们测试了融雪季节潜在径流（R），地下蓄水量变化（ΔS），以及其他水预算组件融雪率（SM _{- [R} ）和定时（SM_吨使用多元线性回归和全局灵敏度分析（GSA））。回归结果证实R受sm _r和sm _t竞争影响。在两个位置上，ΔS对sm _t的敏感性高于sm _r，而R对P301的sm _r和NR1的sm _t更为敏感，这反映了NR1的能量限制。GSA分析反映了R的回归，确认在NR1上sm _t比P301更重要。这项工作表明，较早融雪的径流增加可能抵消了由于融雪速度较慢而造成的径流损失，而且这一过程是由PAWS和能源可用性所介导的。这些结果表明，[R将是在未来的变化更敏感SM _[R和SM _ŧ在更大的爪子和可用能量的网站。